ECG Case 097

Rate:

Rhythm:

• Regular
• Sinus Rhythm
• Alternating QRS Morphologies

Axis:

Intervals – QRS Complexes Labelled in Red

• PR – Short at ~110ms
• QRS – Normal at 100ms
• QT – 340ms

Intervals – QRS Complexes Labelled in Green

• PR – Normal at ~140ms
• QRS – Normal at 80ms
• QT – 320ms

Additional:

• Alternating variation in QRS voltages
• Alternating variation in T wave voltages in right precordial leads
• Subtle delta waves seen in the complexes labelled red in the right precordial and inferior leads

Interpretation:

• Alternating pre-excitation / accessory pathway conduction with sinus conduction

The EP members of our team agree this is likely a weak left sided pathway with classical intermittent pre-excitation which usually confers a benign prognosis in the setting of atrial fibrillation.

For a great overview article on pre-excitation and paroxysmal SVT check out: